I'm sure most scientists would not have the patience to try, and most probably could not do it even if they did try. But that inability has nothing to do with the level of understanding attained by the scientist, or with the probability that the theory is valid. It has everything to do with the communication skills of the people involved, the ability of the scientist to clearly say what they mean, and the ability of the listner to understand it. This kind of communication is really hard. I think I'm pretty good at it, and I've been working on that ability as a public speaker for many years. But I still find myself sometimes unable to communicate ideas that are just too mathematical, or too technical, to translate into plain English.

Along the same lines, I disagree here too. In fact, I think the opposite is likely to be true. Really good science is really hard to understand if you have no experience or expertise to draw on. How can somebody explain, for instance, string theory, to people who have, at most, completed high school algebra? Brian Greene did about as good a job as one could with Elegant Universe, but it's way short of the mark for really explaining what string theory really is. That's because, no matter how many spiffy drawings we make, visualizing a compact Calabi-Yau space is just not in the cards for any non mathematician, and probably not for most who are mathematicians. Understanding theories at any real level requires an understanding of the fundamental principles involved, which in turn requires an education & experience relevant to the question. The ability to explain a theory, in practice or in principle, has nothing to do with the validity of the theory, or with its scientific value.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell